Ah, my mistake. I returned the original String for i===0. Thanks!

Description says:

if i === 0 : returns an empty string;

Test-cases expecting a 0-length string are testing left$( aString, 0 )

I don't really understand what testcase might cause the message Expects a 0-length string - Expected: , instead got: Keep It Simple Stupid

I read it as: when i is an empty String, $left/$right should return an empty String. If I implement it like such and test it myself (eg. Test.assertEquals( left$('Hello o o o World', ''), '');), my test passes but the aforementioned test still fails.

Could you explain which case this is supposed to test?